Conditional Eddies, or Clumps, in Ion-Beam-Generated Turbulence

Abstract

Low-frequency electrostatic fluctuations are investigated experimentally in an unmagnetized plasma. The turbulence is generated by ion-ion-beam instabilities. Real-time signals are recorded and investigated statistically on a conditional basis. The formation and propagation of structures with a relatively long lifetime in terms of the average bounce period is observed. Particles bouncing in the potential well associated with these "eddies" will necessarily remain correlated for times determined by the eddy lifetime. The results thus provide evidence for clump formation in plasmas.